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Linear i.p.d. adjustment v folding

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#1 25585

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Posted 16 December 2019 - 11:29 AM

Which do you prefer? Which is better?

 

Older Baader/Celestron & Takahashi were linear. The Long Perng Newtonian bv is linear. Any others?



#2 Eddgie

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Posted 16 December 2019 - 05:23 PM

The linear focusing is not so much a design option as it is a design choice driven by the optics inside the BV.  Most commonly (as far as I can see), the linear IPD is used when mirrors are used in the BV, and the folding design is mandated by the use of prisms because to use the linear design with prisms, the prisms or beam splitter would have to be much larger and heavier to allow the wide lateral movement necessary to accommodate a wide range of IPD.

 

I have never seen a prism based astronomy unit that uses lateral focusing (but I am the first to admit that I have not seen every astronomy binoviewer ever produced). Certainly, there are none in production today (for astronomy).

So, this is not so much a question as to which is better in that it is generally set by whether the BVs use mirrors or prisms.

 

As far as that goes, Dennis says that the mirror units are sharper, and I would say that if they are, it is probably just because that whatever units he have used probably had higher quality mirrors than may of the prisms in the prism units he has used.  Otherwise, there is no particular reason that the mirror should be sharper other than the quality standard set (and maintained becuase you can set any standard you want, but you only realize that standard if you agressively test for it!)  Also, prisms can have extremely high transmission with relatively simple coatings, and there is little danger of degradation the way there is with a lot of mirrors and regular proteced aluminim would not have the same transmission as the prisms in a regular binocular. 

So, which is better?   Both accomplish the same goal, but the choice of what to use is (I think) driven by wheter it is prism or mirror based.  In other words, if you think this or that linear unit is what you want, most are mirror units.  If it is a prism you want, practically all of them are hinged IPD.

 

I know that does not answer your question exactly, but it was not intended to.. It was intended to say that to compare them as choices, one is in most cases comparing one design approach to another, so it is not simply "Which IPD adjustment do I like better."

 

I have used both types, and once set for me, it is almost never touched again, so how it accomplishes the IPD spacing, as far as I am concerned, it could be welded in place, making the question of how it got the spacing kind of irrelevant. 

 

(This though would be one advantage of the mirror units. Some are rack and pinion spaced, and would more likely hold the IPD adjustment, but this has never been an issue for me personally because even if IPD is knocked out, it is trivially easy to re-set in the hinge design.)


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#3 25585

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Posted 16 December 2019 - 08:10 PM

Thanks Eddgie, I did not know there was more to the designs than appearances.  



#4 Eddgie

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Posted 16 December 2019 - 09:25 PM

Thanks Eddgie, I did not know there was more to the designs than appearances.  

Yeah, I mean it was an interesting question and I could absolutely see some desire to see if people might have reasons to choose one over the other.  

 

I hope I did not over-answer (I get wordy a lot) but because I did think it was an interesting question, I thought it deserved a detailed response.

 

I am pretty sure all of the units you mentioned used mirrors and hence all used linear IPD.  (The Orion appears to use a collimator of some sort and mirrors, so a hybrid design). 



#5 Bob4BVM

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Posted 19 December 2019 - 01:01 AM

 Eddgie give a good explanation of the why of linears

In case anyone is wondering, this is what it looks like inside...

 

Those big brass blocks on either side each carry a mirror, and are suspended on a set of 3 collimation screws.

If you are the adventurous type, they are remarkably easy to collimate perfectly while apart, jus t pop a laser in each EP holder, the beams pass off the mirrors, thru the cube beamsplitter and projected to a distant wall target. Just adjust the mirror screws til the spots merge, bingo...  Thank you to Mr. Glenn LeDrew for his help with this !

CS

Bob

 

IMG_4490 Clsd-s.jpg IMG_4492 Int1-s.jpg  NikonZooms,B+L BVer.jpg


Edited by Bob4BVM, 19 December 2019 - 01:05 AM.

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#6 denis0007dl

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Posted 19 December 2019 - 01:24 AM

 

In case anyone is wondering, this is what it looks like inside...

 

Bob

 

attachicon.gifIMG_4490 Clsd-s.jpgattachicon.gifIMG_4492 Int1-s.jpg attachicon.gifNikonZooms,B+L BVer.jpg

Bob, thats is absolutely not correct!

You have tottaly different binoviewer, and linear binoviewer have different optic design wink.gif



#7 Bob4BVM

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Posted 19 December 2019 - 01:51 AM

Bob, thats is absolutely not correct!

You have tottaly different binoviewer, and linear binoviewer have different optic design wink.gif

OK then  Denis, you are the expert, so I will stand corrected.

 

I thought the discussion was about BVers with a linear IPD adjustment, as opposed to hinged IPD adj.

 

These B&L units do have a linear (sliding) IPD adjustment.

 

Do I have a 3rd type ?  What would you call it ?



#8 denis0007dl

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Posted 19 December 2019 - 02:32 AM

OK then  Denis, you are the expert, so I will stand corrected.

 

I thought the discussion was about BVers with a linear IPD adjustment, as opposed to hinged IPD adj.

 

These B&L units do have a linear (sliding) IPD adjustment.

 

Do I have a 3rd type ?  What would you call it ?

Your bino have same optical system as have Takahashi TwinView, old Celestron/Baader Angled binoviewer, and Carl Zeiss old Angled binoviewers, but in different way: instead prisms ob both sides, B&L use mirrors.

 

Your bino have small cube beamsplitter, and 2 flat mirrors, tahts it, very simple.

 

So called new linear binoviewers from TS, Kasai, Long Perng, Orion etc, use much more complex system: 9 lenses and 3 mirrors (they are same binoviewers under different brand names).

 

B&L binoviewer takes light path, while new linear ones dont.

 

If you compare optical performance your B&L bino vs above mentioned new TS, Kasai, Long Perng, Orion etc binoviewers, you will see how easily B&L outperform them. But not only that B&L is optically better, but have waaay better mechanically as well.

 

I dont have some specific name for that design.

 

Kind regards

CS

Denis


Edited by denis0007dl, 19 December 2019 - 06:34 AM.


#9 denis0007dl

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Posted 19 December 2019 - 02:43 AM

Which do you prefer? Which is better?

 

Older Baader/Celestron & Takahashi were linear. The Long Perng Newtonian bv is linear. Any others?

In my experience, from linear ones, Carl Zeiss angled one is best of all by far.

 

From folding binoviewers, best are Baader Mark V, Carl Zeiss, and Leica, others are not worth to mention IME.

 

If I had to choose which I like best, I would say I like both very much, but folding ones would be option if I have to choose only one design.

 

Kind regards

CS

Denis



#10 Eddgie

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Posted 19 December 2019 - 08:51 AM

Denis, I think it is semantics and marketing. 

 

The "Linear" binoculars just use that marketing description to denote the fact that they use linear IPD adjustment, but any binoviewer that uses linear IPD adjustment could (and should) be called linear binoviewers as opposed to hinged binoviewers.  The use of the collimator type approach makes them different from standard binoviewers, but that could be accomplished without having to use linear IPD adjustment.  

 

In the context of the OP's post, Bob4BVM was not saying he had hybrid linear binoviewer, but rather a binoviewer with linear IPD adjustment rather than a binoviewer with hinged IPD adjustment. 

 

 

(I think they used the "Linear" term in their marketing just to deal with the fact that they look so much different than the hinged designs.   The real differentiation is that they are zero light path length binoviewers, but most people would not understand that term, but they would know that they don't look like the other binoviewers on the market, so I think the marketing people just chose to highlight the linear IPD function to both paint it as "Different" and possibly better, and to explain why it looks so different than the competitive offerings. Linear does not make it better though, and the primary marketing difference between these and traditional binoviewers is the zero light path length.  People just would not know what that meant though, so "Linear" sounds new and bold and snazzy. )  


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#11 denis0007dl

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Posted 19 December 2019 - 10:10 AM

Denis, I think it is semantics and marketing. 

 

The "Linear" binoculars just use that marketing description to denote the fact that they use linear IPD adjustment, but any binoviewer that uses linear IPD adjustment could (and should) be called linear binoviewers as opposed to hinged binoviewers.  The use of the collimator type approach makes them different from standard binoviewers, but that could be accomplished without having to use linear IPD adjustment.  

 

In the context of the OP's post, Bob4BVM was not saying he had hybrid linear binoviewer, but rather a binoviewer with linear IPD adjustment rather than a binoviewer with hinged IPD adjustment. 

 

 

(I think they used the "Linear" term in their marketing just to deal with the fact that they look so much different than the hinged designs.   The real differentiation is that they are zero light path length binoviewers, but most people would not understand that term, but they would know that they don't look like the other binoviewers on the market, so I think the marketing people just chose to highlight the linear IPD function to both paint it as "Different" and possibly better, and to explain why it looks so different than the competitive offerings. Linear does not make it better though, and the primary marketing difference between these and traditional binoviewers is the zero light path length.  People just would not know what that meant though, so "Linear" sounds new and bold and snazzy. )  

Eddgie,

 

mostly agree, but, Bob4BVM wanted to show how looks his binoviewer inner system, so, its important to understand that B&L binoviewer is tottaly different vs new so called Linear ones mentioned before, so people will know main differences I explained between them, becasue, I am sure some readers tought/could consider that they are absolutely same design made etc, so commenting 

"In case anyone is wondering, this is what it looks like inside"

makes sense to explain.

 

Nothing else ;)

 

Now about how they should be called, let it be like sellers calling them, for easier recognizing.



#12 CharlieB

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Posted 19 December 2019 - 05:10 PM

The Zeiss microscope bino head has a linear IPD adjustment.  The mechanism is a little stiff, but works just fine for my needs.  One thing I have noticed is that there is a slight focus shift when changing IPD.  I used to use a cheapo Celestron binoviewer for 1.25", but I didn't care for it.  The optical train was never in proper alignment.  The Zeiss is built like a tank and even with 30x eyepieces, alignment is perfect. 

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#13 Bob4BVM

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Posted 19 December 2019 - 10:45 PM

Eddgie,

 

mostly agree, but, Bob4BVM wanted to show how looks his binoviewer inner system, so, its important to understand that B&L binoviewer is tottaly different vs new so called Linear ones mentioned before, so people will know main differences I explained between them, becasue, I am sure some readers tought/could consider that they are absolutely same design made etc, so commenting 

"In case anyone is wondering, this is what it looks like inside"

makes sense to explain.

 

Nothing else wink.gif

 

Now about how they should be called, let it be like sellers calling them, for easier recognizing.

Denis,

Just so you know I am fine with your reply to my post above. I see what you are saying, that it is totally different from the 'new' zero lightpath "linear BVers"

I appreciate you clearing up, in case some may mix up the old microscope-head BVers with the complex "linear' ones.

 

I also appreciate your comments on the B&L units. I have two of them, one is a 3" nosed unit with 1-2X zoom in nose. That one is for my 6" RFT 'frac which has a very heavy 3" crayford focuser.

Other one I converted to 2" nose for use in other more standard scopes.

Both of them provide excellent images ! :)

CS

Bob


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#14 denis0007dl

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Posted 20 December 2019 - 04:44 AM

Denis,

Just so you know I am fine with your reply to my post above. I see what you are saying, that it is totally different from the 'new' zero lightpath "linear BVers"

I appreciate you clearing up, in case some may mix up the old microscope-head BVers with the complex "linear' ones.

 

I also appreciate your comments on the B&L units. I have two of them, one is a 3" nosed unit with 1-2X zoom in nose. That one is for my 6" RFT 'frac which has a very heavy 3" crayford focuser.

Other one I converted to 2" nose for use in other more standard scopes.

Both of them provide excellent images ! smile.gif

CS

Bob

No worries Bob, you are welcome.

 

Yep, I know, they are really excellent binoviewers, espeically mechanically if you compare them vs nowdays mostly plastic made ones.

 

Kind regards and all best

CS
Denis




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